Abstract Body: Background: Tissue-engineered vascular grafts (TEVGs) are promising alternatives for peripheral artery bypass, but limited endothelialization and graft stenosis remain challenges. We previously showed that UPI peptides disrupt epsin–VEGFR2 interactions, prevent VEGFR2 internalization, and that local delivery enhances graft endothelialization. However, extended delivery is likely needed in patients. This study embedded peptide-loaded microparticles within luminal coatings for sustained delivery and evaluated their effects in vitro and in vivo. Further, we hypothesize that graft remodeling and cell infiltration within the graft wall will be greater for fibrinogen vs. gelatin coatings.

Methods & Results: Poly(DL-lactide-co-glycolide) (PLGA) microparticles encapsulating UPI peptides (2 mg/g peptide/PLGA) were prepared via a double emulsion, with scrambled peptide and water-only as controls. After lyophilization, microparticles were characterized by SEM, with diameters smaller than capillaries (6.62±4.1 µm). Peptide encapsulation was confirmed using FITC-labeled UPI. Sustained peptide release was observed over 5 days, with continued low-level release thereafter. Microparticles were incorporated into fibrinogen and gelatin coatings within electrospun PCL conduits. A 20-gauge needle template was used for this process because it produced the most consistent coatings and a thin 30.05 ± 1.76 µm gelatin coating (n=3), as measured by optical coherence microscopy. Cryo-SEM demonstrated uniform microparticle incorporation and a smooth luminal surface with no delamination. In vitro endothelialization using GFP-positive human umbilical vein endothelial cells (HUVECs) showed enhanced cell attachment and spreading on coated conduits with UPI peptides after 3 days compared to control. In vivo grafts containing UPI-loaded coatings remained viable within rat aortae after 4 weeks with no evidence of stenosis. Preliminary results surprisingly showed limited remodeling for gelatin coatings (n=3) but good remodeling for fibrinogen coating (n=1). The in vivo studies are ongoing.

Conclusion: These results demonstrate that microparticle-based luminal coatings enable sustained UPI peptide delivery and promote HUVEC attachment. While gelatin coatings supported enhanced HUVEC attachment in vitro, fibrinogen coatings performed better in vivo. This sustained-delivery strategy is especially relevant clinically where graft endothelialization occurs over extended timeframes.